On June 26, the US Supreme Court denied New Mexico’s petition seeking to institute an original action against Colorado for the 2015 Gold King Mine spill. An original action in the US Supreme Court is a lawsuit between states. Invoking that rarely used procedure, New Mexico sought to hold Colorado liable for the Gold King Mine spill. New Mexico asserted claims under the intricate provisions of the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA) and the Resource Conservation and Recovery Act of 1976 (RCRA). New Mexico also sought analogous relief against Colorado under federal interstate common law.

Attorneys assisting the State of Colorado, successfully argued that the US Supreme Court should not entertain New Mexico’s novel lawsuit. As explained in Colorado’s briefing, New Mexico’s RCRA claim failed because a CERCLA response action had been initiated to address the relevant hazardous substance release. New Mexico’s CERCLA claim failed, Colorado argued, for a number of reasons, including that once a site is under investigation under CERCLA authority, several of New Mexico’s claims are barred because they would interfere with the CERCLA investigation and remedy decision making. Colorado additionally argued that Congress displaced New Mexico’s putative federal common law claims through its enactment of comprehensive environmental statutes, most importantly the Clean Water Act, but also CERCLA and RCRA.  Finally, Colorado’s briefing also explained that Colorado should not be held liable for its regulatory activities in remediating and managing abandoned mines.

The Gold King Mine spill occurred in August 2015 after a contractor for the US Environmental Protection Agency (EPA) breached a collapsed mine portal at the Gold King Mine in the mountains near Silverton, Colorado. The breach released roughly three million gallons of acidic mine water into the Animas River.  The release received national attention because, for a time, it turned portions of the Animas River yellow from the oxidation of dissolved iron in the escaped water.

US EPA studies performed following the release concluded that water quality returned to pre-event conditions within two weeks after the Gold King Mine plume passed. Additionally, there were no reported fish kills in the affected rivers, and post release surveys by several organizations found that other aquatic life do not appear to have suffered harmful short-term effects from the Gold King Mine plume.  US EPA and Colorado continue to monitor the potential impacts from the Gold King Mine spill.

Remediation efforts at Gold King are ongoing. Last year, US EPA—which has taken responsibility for the spill—listed Colorado’s Bonita Peak Mining District (including the Gold King Mine) as a Superfund site.  In a statement, US EPA Regional Administrator explained the benefit of that listing:

Listing the Bonita Peak Mining District on the National Priorities List is an important step that enables EPA to secure the necessary resources to investigate and address contamination concerns of San Juan and La Plata Counties, as well as other downstream communities in New Mexico, Utah, and the Navajo Nation.

Colorado’s victory at the US Supreme Court protects Congress’s carefully constructed statutory scheme for the effective management and remediation of water pollution across the country. It also protects Colorado’s sovereign ability to remediate abandoned mines.